A work permit is the permission to take a job within a foreign country. It may also be a permit given to minors allowing them to work legally under child labor laws. Within an industry, a work permit may be required to execute certain functions within a factory outside normal operational tasks (such as maintenance tasks) - in some places they might be called Permit to Work (PTW).
Currently, every EU country has a different process for granting work permits to nationals of non-EU countries. To address this issue, the European Commission began work in 1999 on developing an EU-wide process for the entry of non-EU nationals into the work force. In October 2007, they adopted a proposal to introduce a work permit similar to the United States' "Green Card" program, called the "Blue Card". It is similar to the UK's Highly Skilled Migrant Programme, with the exception that it will require an employment contract in place prior to migration. After two years in the first country, the migrant will be allowed to move and work in another EU country, and can sum the number of years spent in the EU for purposes of residency. This new card will abolish work permits across the EU and centralize the issuing from Brussels. 
The procedure to get a work permit is quite elaborate since the applicant should prove that no French jobseeker fitted the position.
There are seven standard ways to apply for a work permit in the United Kingdom: the Business and Commercial Arrangements, the Training and Work Experience Arrangements, the Sports people and Entertainers Arrangements, Student Internships, GATS, Ancestry Visa and the Sectors Based Scheme. Each of these involves its own application process, and generally requires a job offer from a UK employer. The UK has stopped accepting work permits in many other categories.
The UK work permit system is currently being replaced by a new points-based immigration system.
However, Nationals of certain countries will have to also apply for clearance to arrive in the UK. It is very important to note that the UK Company offering you a position must have a sponsor license in order to issue you with a certificate of sponsorship before you can apply for the visa. 
In general, the United States does not require work permits for adult citizens. However, certain aliens are required to have an Employment Authorization Document from the United States Citizenship and Immigration Services (USCIS) of the Department of Homeland Security (DHS).
The federal government of the United States does not require work permits or proof-of-age certificates for a minor to be employed. However, the possession of an age certificate constitutes a good faith effort to comply with minimum age requirements of the Fair Labor Standards Act of 1938. The United States Department of Labor will issue a "certificate of age" if the minor employee's state does not issue them, or if the minor is requested by his or her employer to provide one. Several states are not listed in 29 C.F.R. 570.9(a), such as Alaska, Arizona, Idaho, Kansas, Mississippi, South Carolina, Texas, and Utah, and thus their certificates may not meet the requirements of 29 C.F.R. 570.5(b) as being evidence of compliance with the Fair Labor Standards Act.
Many states also require them for workers of certain ages. In some states, for example New Jersey, permits are only required for minors 14 and 15 years old, while others such as Massachusetts require, at least in theory, work permits for all minors until they turn 18 years of age. In some states, enforcement is strict. Permits are usually issued through the school system the minor attends, and typically at a minimum is conditioned on enrollment in high school with regular attendance (no chronic absenteeism, tardiness, or truancy). Some states such as New York and Indiana require high school students with part-time jobs to maintain a certain grade point average. Minors who are working are usually restricted in the number of hours each day or week they are permitted to work as well as the types of jobs they may hold.
There are three categories of South African work visa or permit available to a foreigner each with its own set of specific requirements all assisting in immigration to South Africa or working in South Africa. These are the General Work Visa/Permit, the Critical Skills Work Visa/Permit and the Intra-Company Transfer Work Visa/Permit.  Due to recent immigration law changes (May, 2014), the obtaining of work visas or permits in South Africa has become much more arduous. Furthermore, these work permits are now referred to as visas.
General Work Visa/Permit - The basis of a general work visa/permit is that a firm offer of employment has been made by a prospective employer to a foreigner after such employer has unsuccessfully exploited the local labour market in attempting to procure the needed skills, experiences or qualifications equivalent of such foreigner.
Critical Skills Work Visa/Permit - A critical skills work permit may be issued to a foreigner who possesses critical skills or qualifications and is able to demonstrate with supporting documentation in the form of testimonials, publications. This is based on a list published by the Department of Home Affairs in South Africa called the Critical Skills List  A letter of motivation from an authoritative body to substantiate the benefits that those skills will bring to South Africa. This critical skills work permit is granted for up to five years years and may be renewed for a further period, if required. This visa type replaces the previously issued Quota Work Permit and the Exceptional Skills Work Permit.
Intra-Company Transfer Work Visa/Permit - An intra company transfer work permit is issued to a foreigner who is normally deployed or seconded to South African branch, subsidiary or associate office of a corporate entity aboard. There are strict controls to ensure that the foreigner remains employed in his or her specific position during the tour of duty. This type of visa is only valid for two years, and often no extension is possible. Also, any applicant must have first worked for a minimum of 6 months in the employ of the company’s foreign office before applying to relocate and immigrate to the South African branch. 
In Singapore, the work permit process citation needed]. There are several kinds of work permits, and the type accorded generally depends on the salary range of the position, as well as on skills (including education), work experience, and the type of job being applied for. These work permit types include the Employment Pass (monthly salary of at least S$4,000), S Pass (monthly salary of at least S$2,800), and "Work Permit" (generally for unskilled workers).[
Another kind of work permit available in Singapore commonly known as the EntrePass and is especially geared towards entrepreneurs who might not pass the stringent requirements regarding education and salary. The EntrePass is for foreign entrepreneurs who are planning to start up a business in Singapore. The entrepreneur must be actively involved in operations of the business. Candidates can apply for this anytime up until 6 months after they registered the business. Generally EntrePass are awarded to individuals whom have either have a proven track record of running successful businesses or whom have an innovative idea. The Singapore Personalised Employment Pass, also known as PEP is a special type of Singapore work visa issued to individuals based on their own merits. The issuance of the PEP is managed by Singapore’s Ministry of Manpower. The PEP is independent of any employer, rendering a PEP holder the flexibility and freedom to switch employers without having the pass revoked. The PEP holder is also entitled to stay in Singapore for up to 6 months in between jobs and to evaluate career opportunities. It is issued for a period of 5 years, and non renewable thereafter. But, since December 2011, PEP has been discontinued by the Singaporean Authority.
A work permit system is a formal written system to control certain types of work identified as potentially hazardous. The terms "P.T.W.", "permit" or "work permit" refer to the form used by a company to meet its needs. These systems aim to ensure proper planning and consideration of the risks involved in a particular job, at a specific time and place, with designated precautions. 
It is usually categorized in "hot" work permits and "cold" work permits. Hot works are those where there is a potential of generating fire or extreme heat, cold ones are all the others.
Several different types of visas are available for immigrants. The applications are assessed through a point based system. If an individual has the right skill set and qualifications, they can apply for industries listed as being in need of workers. There are several work permit visas available as well, the most prominent being the Employee sponsored visa called the Subclass 457 work visa. This is a contract based on temporary visa offered to those with an employment contract already awaiting them in Australia.
- "Towards a Common European Union Immigration Policy". European Commission. Retrieved 2007-03-03.
- "EU Blue Card to encourage highly-qualified non-EU citizens to work in the EU". European Commission, Irish Press Office. Retrieved 2007-03-03.
- Alain-Christian Monkam, "How to get a work permit in France', Village de la Justice, 2011, http://www.village-justice.com/articles/permit-France,11079.html
- "Working in the UK - Work Permit Arrangements". Government of the United Kingdom. Retrieved 2007-03-03.
- "UK Work Visa - Visa Service & Advice Online". www.migrationexpert.co.uk. Retrieved 2017-01-23.
- "Youth & Labor: Work Permits & Age Certificates".
- 29 C.F.R. 570
- "Work Permits in South Africa". Immigration South Africa™. Retrieved 2015-07-08.
- General Work Visas in South Africa
- South Africa's latest Critical Skills List (PDF)
- Critical Skills Work Permits in South Africa
- Intra-Company Transfer Work Permits in South Africa
- "Passes and Visas (Singapore)". Singapore Ministry of Manpower. Retrieved 2012-05-06.
- "Personalised Employment Pass (Singapore)". Singapore Ministry of Manpower. Retrieved 2012-05-06.
- "Guidelines on permit to Work (P.T.W.) systems" (PDF). International Association of Oil & Gas Producers. Retrieved 2012-09-18.